A wide variety of machinery is available for making stranded wire, for example, of the type which subsequently is insulated for use in electrical installations. Such operations have been performed in the past on machines in which the spools of wire were rotated about a central core wire to produce a so-called concentric strand configuration. By a "concentric" strand is meant one wherein the strands of each successive layer surround the core wire rest side-by-side, and have some back-twist to reduce the tendency of the constituent wire to open up. The mechanical and dynamic problems inherent in such machines include high centrifugal forces and high friction forces, which must be accomodated by reduced operating speeds, reinforced structures, and complex structures. Additionally, the finished product tends to be difficult to control as to surface condition, and uniformity of size and weight. Such considerations have led to the use of other means to produce stranded wire. For example, so-called bunchers, particularly of the "reverse twist" type, have been modified to guide the constituent wires into the geometric configuration of a concentric strand, rather than the comparatively random configuration of a bunch strand. Typically, however, the products of such operations exhibit characteristics which are deemed undesirable in the industry. For example, unidirectional lay of successive layers of wires, insufficient back-twist in the individual strands to ensure dynamic retention of the constituent wires in place, and damage to the constituent wires caused by the dies that are used to effect closure of the wires and monitoring of the overall diameter of the finished strand, are objectionable results of such processes. These are among the reasons for the better alternative having been sought in apparatus such as the so-called "barrel strander". In such machines, a row of spools containing single-end wire, alone or in combination with a previously stranded core where a multi-layered strand is to be produced, are gimble-mounted on support bearings along the central axis of an apertured outer cylinder, so that the latter may revolve about them while they remain relatively stationary. The wires may then be paid off from the spools through pulleys arrayed on the inside of of the cylinder, through a closure die to a take-up reel for the finished strand. However, in order to achieve the high barrel rotation speeds which are a necessary concomitant of the high production rates which are desired, it is necessary to minimize as far as possible the weight and diameter of the barrel, so that centrifugal forces will be minimized as well. Correspondingly, this presents engineering problems in accomodating spools of individual size such that comparatively long strands may be produced, and in mounting them in tandem down the length of the axis of the interior of the barrel. The result is that machinery of this type does not lend itself to the production of materials which are susceptible to deformation as a consequence of the resulting torsional and friction forces, such as finer strands made from malleable material such as copper, since the quality, size, weight, surface, and electrical variations which result are not up to standards desired by industry. Further, in the use of stranders of the barrel type, when an individual spool of wire runs out, it is the industry practice to connect the end of the wire on the spent spool to the beginning of the wire on a replacement spool. This is done by silver-soldering the two together or utilizing other connection means, which are tedious and time-consuming to perform. The structural configuration, and size limitations of such machines render alternative procedures impractical.
Accordingly, it is an object of this invention to provide means which will produce a concentric configuration of wire strands.
Another object of the present invention is to provide such means to minimize weight, diameter, resistivity, and surface variations in the production of articles made from comparatively soft materials.
Still another object is to provide stranding means in which changeovers in direction and/or lay-length may be easily changed.
Another object is to produce such means which are easier to load than prior art stranding machines.
Yet another object is to satisfy the foregoing objectives with means which have low weight and simple construction, to minimize centrifugal and other dynamic forces when the machine is in operation and to facilitate access to its various constituent parts for its operation and maintenance.